block

[userbmx1315]

has anyone, herd of or have, welded a block? bought a stroker with a crack in it. was going to use all the parts in it but as to my luck, the block i wanted to get machined had a hole in it also.

 

[5-90]

has anyone, herd of or have, welded a block? bought a stroker with a crack in it. was going to use all the parts in it but as to my luck, the block i wanted to get machined had a hole in it also.

Where's the crack? You can weld exterior cracks and breaks if you have a welder who knows his shite (and uses the right rod and technique - you'll need a good high-nickel rod, and it's a two-man job. I've been the second man a couple of times...) but it gets complex after that. The deck can usually be welded and ground flat - if it's in the cylinder bore, either sleeve the block or melt it down, as it's shot.

 

[tbburg]

It's really only common on expensive industrial gear, very rare equipment, or for a rare car(original block from a number-matched vette, etc) It can be done to about anything, but is expensive. In most cases, it's cheaper to start over with a new core, since the machining is usually less intensive. The block usually needs to be totally re-machined(as in line-bored to start) If a cylinder is cracked, it's usually welded, overbored, then sleeved and final bored/honed.

Where's the hole? Through the jacket, or through a cylinder? If it's just a water jacket, you may be able to get it brazed back together without too much hassle.

 

[userbmx1315]

its beside the water pump. hair-line crack bout 2-2.5 inches

 

[winterbeater]

IIRC, cast iron also needed to be stress relieved (heat treat operation) after welding. Can't non stress areas be brazed?

 

[5-90]

IIRC, cast iron also needed to be stress relieved (heat treat operation) after welding. Can't non stress areas be brazed?

Brazing that area would probably be more effective (relatively low stress,) but you'll still have to stop-drill it beforehand, and grind it nice and flat afterwards. Heat-treatment/stress-relieving should not be necessary for a braze job.

For a weld, you stop-drill, then one guy heats the area up with a torch to 1000-1200*F. Once it's there (Tempil sticks work well for this,) the welder starts to tack the thing back together - generally it's 3-4 short tacks, then the welder backs off and the torchman reheats the area around the weld. Repeat until the crack is filled, with a stagger to the weld/stitching (usually 3-4 passes for full coverage - this prevents distortion due to the weldment.)

Once the weld is filled, the torchman gets the area around the weld - and the weld itself - heated fairly evenly, then you allow it to cool fairly slowly to relieve stresses caused by welding in the HAZ. It does take a while, and it does get spendy.

If you feel up to accurate control of a good flat bastard or double-cut mill file, you can braze it and file it flat afterwards - just pay attention to what you're doing! This should only be used in low-stress areas - the water pump mounting, the oil sump rails, and the like.

 

[go1lum]

If you weld it. Stop drill both ends of the crack. Take a grinder and bevel out the crack. Preheat with a rosebud or other source to at least 500*f. 900* would be better. Stick weld it with 99Ni rod. Stuff isn't cheap. Weld approx 1" at a time. Chip the slag, and peen the hell out of it. The sharp end of a chipping hammer works good. Needle guns also can work pretty good. Check the temperature of the block around the work area. don't let it slip under prolly 900* while you are welding. When you are finished with all of the welding reheat the area to about 1200*f. Then you need a way to slow cool the block. Maybe find some way to pack it in kitty litter, sand, or try to wrap it up real good in a blanket. Preheat and post heat help take the stress out of the casting, and slow the cooling rate which helps prevent cracks.

If braze it preheat is still never a bad idea. It is usually beneficial when it comes to any joining process. Still stop drill each end of the crack and bevel out the joint. Some sort of slow cooling wouldn't hurt either.

 

[Curtis_H]

I have helped a friend weld the block on an old farmall, we did as many of you stated. Stop drilled both sides, beveled the crack, pre heated, stich weld, heat, weld, peen, peen, more peening, then re-heated, then took it out back with the skid loader and put it in a hole in the ground about 3 feet deep and covered it with sand. Left it there for 2 days, came out beautifully. Just be damn sure to get all that sand back out or :explosion

 

[asp]

john has this covered pretty well.

http://www.lincolnelectric.com/knowledge/articles/content/castironpreheat.asp